The exclusive agreement “gives our customers a way to get into alternative fuels and get a return on the investment they make, like immediately. It’s a great commercial answer for alternative fuels,” Navistar CEO Dan Ustian told CNBC, after his company reported 2012 earnings guidance of $5 to $5.75 a share, below analyst expectations of $5.90.

Demand for alternative fuel is “over the top,” he said, and to meet it he predicts the company will get new trucks on the road “within the next six months.”

Pickens, CEO of BP Capital Management and a longtime advocatefor putting natural gas in American trucks, said in the same interview that Clean Energy will build more than 100 natural gas filling stations on several major U.S. highways this year.

“You’re saving $1.50 a gallon” using natural gas, Pickens said. “Some of these trucks are running 20,000 to 30,000 gallons a year. The return on it is great. It’s cleaner by 30 percent over diesel, but (the fuel) is also ours. It’s abundant and it’s domestic.”